I agree, Veruka. Dustin had to do something to defuse the fact that Joe had already been with the group of 11, "charming them" and whatnot, and then publicly stated that Dustin had given him an STD (eewwwwhhhh - why say that about YOURSELF, let alone someone else on the first day you're meeting people). Going around and trying to be pleasant was a good move by Dustin to show "I'm a human being, and what Joe said about how he tried to destroy my life is WHO JOE IS, so let's all get JOE the heck out of here."
I hope Dustin does well. I feel for Dustin and anyone else who has an ex that cackles with glee and relishes telling others about how much pain they causes a former partner. BTDT